Adhesives, including pressure-sensitive adhesives and structural adhesives, are commonly used to bond parts to assembled articles in industries as varied as, for example, electronics, automobiles, abrasives, medical devices, and optics. For example, structural adhesives can be used in the automobile industry to bond parts such as rear view mirrors to windshields. Or optically clear adhesives can be used to bond optical films, electromagnetic shields, or even touch-sensitive films to electronic devices such as, for example, cellular phones, personal computers or computer tablets. Due to the high cost of the articles and the relatively low cost of the bonded films, it is sometimes desirable to remove the bonded part (debond it) for repair of the article, for modification of the article, for repositioning of the film on the article, or for recycling of the bonded article.
Reworkable and repositionable pressure-sensitive adhesives have been developed for this use. Typically, such adhesives adhere much more strongly to one substrate, such as an applied film, than to another substrate, such as a windshield or electronic display. Thus, they can be removed cleanly from the more expensive product and the applied film can be reworked or replaced. Adhesives are known that can be released by stretching the adhesive in one direction to reduce its adhesiveness. Some of these adhesives are sold under the trade designation, COMMAND, and are available from 3M, St. Paul, Minn.
Shape-memory can be used to debond pressure-sensitive adhesives. U.S. Pat. No. 5,888,650 (Calhoun et al.) teaches the use of a temperature-responsive carrier capable of changing its three-dimensional shape at a first transition temperature and a thermomorphic pressure-sensitive adhesive on at least a portion of at least one surface of the carrier. The thermomorphic pressure-sensitive adhesive is capable of changing its three-dimensional shape at a second transition temperature. By varying the initial shapes of topographies of carrier and adhesive and the relationship between the transition temperatures a wide variety of bonding and debonding properties can be provided.